The present invention relates generally to interface devices between humans and computers, and more particularly to computer interface devices that provide force feedback to the user using actuators.
Computer systems are used extensively in many different industries to implement computer controlled simulations, games, and other application programs. More particularly, these types of games and simulations are very popular with the mass market of home consumers. A computer system typically displays a visual environment to a user on a display screen or other visual output device. Users can interact with the displayed environment to play a game, experience a simulation or xe2x80x9cvirtual realityxe2x80x9d environment, or otherwise influence events or images depicted on the screen or in an application program or operating system. Such user interaction can be implemented through a human-computer interface device, such as a joystick, xe2x80x9cjoypadxe2x80x9d button controller, mouse, trackball, stylus and tablet, foot or hand pedals, or the like, that is connected to the computer system controlling the displayed environment. The computer updates the game or simulation in response to the user""s manipulation of a moved object such as a joystick handle or mouse, and provides feedback to the user utilizing the display screen and, typically, audio speakers.
Force feedback interface systems, also known as haptic systems, additionally provide force feedback to a user of the computer system. In a typical configuration, a host computer implements software such as an application program, virtual reality simulation, or game and communicates with a connected force feedback interface device. The user grasps a user object of the interface device, such as a joystick, mouse, steering wheel, stylus, etc., and moves the object in provided degrees of freedom. The movement of the user manipulatable object is sensed by the host computer using sensors, and force sensations controlled by the host computer are provided to the user object using actuators of the force feedback interface device. Force feedback can be effectively used to simulate a variety of experiences, including an impact of a surface, a pull of gravity, a crash in a vehicle, a firing of a gun, a bumpy road, etc., and can thus supply the mass market of computer users an entirely new dimension in human-computer interaction.
One problem with existing force feedback systems is that the actuators used in the interface device are expensive and/or inefficient. One common type of actuator used is a DC motor, which is quite bulky and expensive. The cost of the actuators tends to be a significant part of the overall cost of a device, and in the low-cost, competitive consumer market, any unnecessary costs translate into higher costs for the consumer. Other types of actuators used include voice coil actuators, in which a coil is moved through a magnetic field. However, in a voice coil actuator, circuit or wires which supply current to the coil flex with the motion of the coil. Such a flex circuit can be expensive since it must maintain reliability over the life over the actuator. In addition, a coil having current flowing through it tends to build up heat, and this heat may require a large heatsink coupled to the coil to be dissipated properly. If such a heatsink is provided with the moving coil, less efficient heatsinks are used to reduce weight and/or bulk of the moving part. Therefore, more efficient, low cost actuators that provide high fidelity force sensations are desirable for use in mass market force feedback devices.
The present invention provides a human/computer interface device and method which can provide low cost and highly realistic force feedback to the user of the device using moving magnet actuators.
A force feedback interface device and method of the present invention is coupled to a host computer that displays a graphical environment, the device including a user object physically contacted by a user and moveable in a degree of freedom. A sensor detects a position of the user manipulatable object in the degree of freedom and provides a sensor signal to the host computer, where the sensor signal includes information representative of the position of the user object. An actuator is coupled to the device or user object and outputs a force on the user manipulatable object or a housing of the device. The actuator includes a magnet and a grounded coil, where the magnet moves approximately within a plane with respect to the coil, and wherein a current is provided in the coil to generate the force. Other embodiments provide a magnet that moves in a linear degree of freedom within a coil housing, or provide an at least partially spherical magnet providing rotary degrees of freedom to a user manipulatable object coupled to the magnet.
Preferably, a microprocessor local to the interface device and separate from the host computer is included in the interface device. The local microprocessor provides a signal to the actuator to output the force, and also receives and parses host commands from the host computer, where the host commands cause the force to be output. A support mechanism is preferably coupled between the user manipulatable object and the actuator, and can provide one or more rotary or linear degrees of freedom. The support mechanism can be a five-bar linkage, a frame that moves linearly, a joint member, or other mechanism. The sensor can be a photodiode sensor, and the user manipulatable object can be a joystick handle, a mouse, steering wheel, or other object.
The embodiment including a frame support mechanism includes multiple bearings positioned between the frame and a ground surface, and each of the bearings preferably provide motion in both of the degrees of freedom. In one embodiment, each of the bearings includes a ball that is positioned between an indentation in the frame and an indentation in the ground surface and which rolls to provide motion of the frame. The magnet of each actuator is coupled to the frame and the coil is wrapped around a projection coupled to a grounded surface. Four actuators can be provided, each of the actuators positioned approximately in a mid portion of each side of the rectangularly-shaped frame. An anti-rotation mechanism can be coupled to the frame to reduce a tendency of the frame to rotate during its motion.
The interface apparatus of the present invention includes several low cost components that are suitable for providing accurate force feedback for the home market and other high volume markets. In contrast with previous use of motors and voice coil actuators, the use of moving magnet actuators in a force feedback interface device allows the interface device to be manufactured inexpensively yet include capability to output high quality, realistic forces.
These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following specification of the invention and a study of the several figures of the drawing.